When developing an oilfield one may for instance use underwater installations and lines up to an turret arranged in a floating unit for instance a vessel. The turret allows the floating unit to rotate in relation to the underwater installation, and thereby the lines running from the floating unit to the underwater installation will not be tangled or experience unnecessary stresses. An example on such a solution is described in U.S. Pat. No. 6,176,193.
The turret is arranged rotating in relation to the vessel, and there are normally arranged swivel means within or on top of the turret construction for transferral of fluids, electric power or signals between the vessel and the underwater installation. U.S. Pat. No. 6,302,048 and WO 9965762 describe such solutions. The turret with swivel means are normally designed for a specific use, for instance for a specific oil or oil/gas or gas field. The swivels and turrets have to be designed for optimum weight and size. Due to the requirements of weight and use of space there is normally limited options for expanding the swivel means with additional functionalities as for instance transferral of additional electric power which were not part of the initial criteria of the swivel means. These additional functionalities are criteria which may arise when the field is partly developed, which arise due to new available technology or development in the field which was not predicted. However, when an additional function of the swivel has to be retrofitted there is very limited space on the turret to add to or adapt the original swivel means to make room for the necessary changes. In addition it is also quite important to achieve a solution where the down time is as short as possible. To disassemble the original swivel means and replacing the whole assembly with another swivel means is not a preferred solution, and is often impractical.
It is therefore a need to develop a solution for transferring electrical power which gives a possibility to add additional transfer opportunities to a turret with an existing swivel means, without the need for extra space on top of the swivel and with as little or no down time for the existing transfer arrangement in the turret.
An aim of the present invention is to fulfil these needs. The present invention as defined in the following claims solves these needs.
The present invention relates to a system for achieving transfer of electric power, and/or signals, between a vessel and an underwater installation. Where one rotating element, the vessel, is connected to the static element and the underwater installation, through a turret, is rotationally attached to the vessel or rotating element. The system may be the only system for transfer between the elements.